1. Field of the Invention
The present invention relates to a microchip and a method of manufacturing the same. More specifically, it relates to a microchip useful for a μ-TAS (Micro Total Analysis System) or the like suitably used for biochemical testing of DNA, protein, a cell, immunity, blood etc., chemical synthesis and environmental analysis and a method of manufacturing the same.
2. Description of the Background Art
In recent years, importance of sensing, detecting or determining a biosubstance such as DNA (DeoxyriboNucleic Acid), an enzyme, an antibody, protein, a virus or a cell or a chemical substance has been increased in the fields of medical treatment, health, food and drug discovery, and there have been proposed various types of biochips and microchemical chips (the biochips and the microchemical chips are hereinafter generically referred to as microchips) allowing simple measurement thereof.
A microchip of several cm to 10 cm square having a thickness of several mm to several cm allows a series of analyses or experimental operations in a laboratory. Therefore, the microchip requires a specimen and a reagent only in small quantities, is at a low cost, exhibits a high reaction rate, allows high-throughput testing or analysis, and enables the user to immediately obtain a test result at a site where he/she has collected the specimen. Such an advantageous microchip is suitably employed for biochemical testing such as a blood test, for example.
A generally known microchip is provided therein with a channel network, referred to as a fluid circuit (or a micro-fluid circuit), constituted of a plurality of sites (chambers) for performing specific treatments on a liquid such as a specimen or a reagent present in the circuit and a fine channel properly connecting the sites with each other. The microchip provided therein with the fluid circuit is employed for performing various treatments such as measurement of a specimen introduced into the fluid circuit and a reagent to be mixed therewith (i.e. movement of the specimen and the reagent to a measuring portion serving as a site for the measurement), mixing of the specimen and the reagent (i.e., movement of the specimen and the reagent to a mixing portion serving as a site for the mixing), movement of the specimen and the reagent from a certain site to another site and the like through the fluid circuit. The treatments performed in the microchip on liquids (the specimen, a specific component in the specimen, a liquid reagent, a mixture of at least two of the specimen, the specific component and the liquid reagent etc.) are hereinafter also referred to as “fluid treatments”. Such various fluid treatments can be performed by applying centrifugal force to the microchip from proper directions.
The aforementioned microchip employed for performing fluid treatments by moving liquids introduced into the fluid circuit to desired positions (sites) therein through centrifugal force can be manufactured by bonding a substrate provided with a groove (recess portion) constituting the fluid circuit and a planar substrate to each other. In general, the two substrates, made of thermoplastic resin, constituting the microchip are bonded to each other by welding through photoirradiation (with a laser beam, for example) or thermocompression bonding.
For example, each of Japanese Patent Laying-Open Nos. 2006-310828 and 2006-076246 discloses a microchip having a fluid circuit formed by bonding a plurality of substrates to each other by photoirradiation or thermocompression bonding.
In welding through photoirradiation, two substrates, made of thermoplastic resin, formed by a light-transmitting substrate and a light-absorbing substrate are overlapped with each other, and light is applied to the substrates from the side of the light-transmitting substrate. When the temperatures of bonded surfaces of the substrates exceed the melting point of the thermoplastic resin due to the photoirradiation, the substrates are melted and bonded to each other.